Questions tagged [weather]

Weather means the atmospheric conditions, including wind, temperature and precipitation, in a specific area at a specific time.

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0 answers
73 views

What could cause false returns on weather radar? [closed]

A flight crew reported false returns on the weather radar on a B777 on one system. The transceiver was replaced, however, during the next flight the crew reported the same on both systems. Can anyone ...
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2 votes
1 answer
129 views

Jet Stream effects at 60.000 ft

Today's airplanes cruise at 40,000 feet. Easterly flight times are longer than their westerly components due to the direction of the jet stream. Comercial supersonic flights did/will cruise at 60,000 ...
5 votes
1 answer
198 views

How is “mountain obscuration” determined?

Living in southeast Washington, ForeFlight often paints large swaths of mountainous terrain to the east as IFR “mountain obscuration”. I live at the foot hills, and often as I look that way, I see ...
2 votes
1 answer
96 views

How impactful is De-icing on flight margins?

A quick google search suggests that deicing is a very expensive activity, with many suggesting it might be 5-10k for both deicing and anti-icing fluid. Given that flight costs typically are lower for ...
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0 answers
74 views

Honeywell 880 weather radar malfunctioning

Is anyone aware of issues with the Honeywell 880 weather radar not painting moisture? We had our original 800 unit go bad on our Falcon 7X, We have installed 3 replacements that have hardware and ...
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2 votes
1 answer
63 views

PTCHY LGT MOD SEV coverage on WX charts?

On GFAs, TAFs, METARs we see PTCHY LGT TURB, MOD TURB, -RA, +RA, etc. I was wondering where could I find the technical definition of these terms? For example the percentage coverage of these weather ...
1 vote
0 answers
233 views

Why did this flight, that usually flies around 40,000ft only fly at around 29,000ft for the route?

Looking at the flight BY6272 BRS-PMI, it was considerably delayed and flew (according to the flight radar app) at 29,000 feet rather than its usual 40,000 for this same route. It is a Boeing 787 ...
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3 votes
3 answers
247 views

Does a plane's service ceiling vary with season/temperature?

Aircraft use barometric altitude, e.g. FL300 is the barometric altitude of 30,000 ft MSL. In winter however, FL300 is actually lower than the absolute altitude of 30,000 ft because of a cold and ...
7 votes
1 answer
636 views

How to determine the base of stratus clouds? [closed]

For cumulus clouds this applies Calculate the 'spread,' where you're taking the current surface temperature and subtracting the dew point. Divide the spread by 4.4 (if temperatures are in °F) or 2.5 (...
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1 answer
60 views

What are dry and saturated lapse rates values or ranges for a rising or lowering parcel of air in degrees Celsius?

Environmental lapse rate average is rounded to 2 degrees celsius per 1000 ft.(Note that environmental lapse rate varies through the day).What about parcel of air lapse rate.? Dry lapse rate is a ...
1 vote
3 answers
450 views

Which countries use qfe field pressure?

I heard that acrobatic flight, Russians, Americans use qfe but is it always the case? Also why doesn't everyone use it? Isn't qfe field pressure better than qnh local pressure... Does a pilot ever use ...
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1 answer
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If while landing ,a surface inversion occured close to the ground would atc or atis know?

A change in temperature, pressure and many factors might happen in a surface inversion.Thus affecting landing performance and calculation.The local peessure might change suddenly as well...
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2 answers
129 views

Who gives us transition level when it varies?

Who gives us transition level when it varies? ATC, ATIS, any others?
1 vote
1 answer
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Why is rare to see landings from East to West at the AJU airport?

Every day at the Aracaju - SE, Brazil Airport (IATA: AJU, ICAO: SBAR) planes take off from West to East and lands from East to West. But in rare occasions they will land from West to East. I think it ...
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20 votes
3 answers
4k views

Why would a pilot need to change their heading when flying through a cold front?

When doing my PPL written review there is a question, simply can't get my head wrapped around the reason why and have searched everywhere. It's definitely a very simple thing, however, I am missing ...
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3 votes
1 answer
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When must ATC give wind variation and gust?

In connection with takeoff and landing, ATC will give the current wind direction and velocity to the pilot. In some cases, ATC will also report the variation in direction and/or current gust (max and ...
-2 votes
3 answers
274 views

Difference between "pressure levels raising on warm days causing lower IA" and "TA being higher than IA on warm days" [duplicate]

IA: Indicated altitude TA: True altitude I have seen this picture before: Concept 1 and I understand this. On cold days, the pressure gradient is shorter which means the indicated altitude at a ...
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1 answer
553 views

Is temperature inversion good or bad?

When there is temperature inversion, I heard that convection is suppressed and hence the layer of air is stable. But I also see the following questions when studying for my PAR: A pilot can expect a ...
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9 votes
1 answer
572 views

Is the pressure change due to volcanic activity a concern?

The recent eruption of the Hunga Tonga–Hunga Ha'apai sent a shockwave so massive that it got picked all over the world by weather stations. This is the pressure detected one in Italy (source), where ...
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1 vote
1 answer
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Formation of Clouds in High Pressure Systems (Western Australia - Perth) [closed]

High pressure systems are normally correlated with stable atmospheric conditions with little to no cloud cover, but due to this minimal cloud cover, doesn't that open up the ocean / ground moisture to ...
4 votes
1 answer
214 views

How far does the lightning detector work at an AWOS station, as reported in a METAR?

I noticed on my local airport's METAR that there was distant lightning to the east. I am near Kansas City. When I looked at radar, the only possible system that could produce lightning was in the St. ...
6 votes
2 answers
420 views

What is considered to be a flight into known Icing?

I am aware that flight into known icing is prohibited if your aircraft is not suitable to fly in icing conditions (unless e.g.: FIKI,...). Given the following example I am wondering if it would be ...
0 votes
1 answer
207 views

What is Tendency of RVR?

What does tendency of RVR (Runway Visual Range) mean and why down and up have the same values? This is from AWOS(Automated Weather Observing System)
5 votes
1 answer
913 views

What does AO2A in the remarks of a METAR mean?

I am familiar with AO2 in the METAR remarks as described in this answer, which means the station is automated and has a precipitation discriminator. I have noticed sometimes there is AO2A in the ...
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3 votes
1 answer
170 views

Will a jet flown on a parabolic arc reach its highest altitude on a warm day or a cold one?

In level flight, on cold days jet-powered planes can fly higher because the air is denser. However, at the same time the true airspeed is lower because of the denser air. At warmer temperatures a ...
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15 votes
3 answers
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Why would "hot gases" from a volcano damage helicopter rotors?

In the ongoing story about someone trying to rescue dogs from a volcano with a drone, I keep seeing variations of this claim repeated: Spanish authorities have dropped food down to the dogs with ...
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1 vote
1 answer
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Station pressure vs. reported altimeter

I must be missing something big. Page 12-5 of the PHAK tells me that a station at 5,000 feet above sea level would convert its 24.92 pressure reading to 29.92. I understand that this helps to track ...
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11 votes
4 answers
4k views

Why are pressure levels raised on warm days?

As I'm studying for the PPL knowledge exam, I had the following note: Pressure levels are raised on warm days and the indicated altitude is lower than true altitude. (source: AOPA) But I don't quite ...
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0 votes
0 answers
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What is inflated wind speed?

According to NOAA, inflated wind speed is "the true wind speed (in knots) adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, ...
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0 votes
2 answers
487 views

Best way to forecast density altitude?

Let's say I'm planning a day trip from a low elevation home base to a warm, mountainous location. I wake up early, check the weather, do performance calculations based on current METARs, and decide to ...
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2 votes
2 answers
907 views

Why is the minimum for VFR 1000/3 while there are VFR weather minimums for every single airspace?

It seems like I have a concept error here. I don't understand why "the VFR min is 1000/3" when I think I would need to check in which airspace I am to then check for its respective weather ...
10 votes
3 answers
2k views

Effect of heat and humidity on take off, descent, climb, and cruise

I am aware of this question, this resource (phak), and this resource that explains the science, but I am looking for a more straightforward answer. I am student pilot and there's a lot of literature ...
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1 vote
1 answer
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What kind of weather conditions would produce turbulence with an intensity of 90 feet per second?

This is the official documentation that we found regarding current commercial airplane design criteria; https://www.law.cornell.edu/cfr/text/14/25.341 It says the criteria for continuous turbulence is ...
3 votes
1 answer
273 views

Why does the Winds Aloft ‘For Use Time’ start before the ‘Valid Time’?

Why is it that a winds aloft forecast normally has a "valid time" that comes in the middle of the "for use" time range? Why don't they just state the valid time as the beginning of ...
1 vote
1 answer
91 views

What does Region @TOP mean on the aviationweather.gov website?

When looking at raw METAR data on the aviation weather center, "@TOP" appears in the text box where you can type identifiers. What does TOP mean?
4 votes
2 answers
253 views

Do airliners get substantially different weather briefings from the rest of us?

Southwest Airlines flights were delayed and cancelled this week due to an outage in their third-party weather provider. I understand if they have a streamlined business process for getting weather ...
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0 votes
2 answers
558 views

How can I calculate the "stability state" of air from a given set of data?

I would like to know the answer for the above question, it is about how to find whether atmosphere is stable or unstable using DALR (dry adiabatic lapse rate), SALR (saturated adiabatic lapse rate) ...
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10 votes
1 answer
3k views

What is the red barb for in the NOAA weather briefing?

Wind barbs are well-defined symbols, but I noticed in my WX briefing that there are now occasional red barbs in the chart. The red appears on both the 5kt and 10kt barbs, and sometimes for largest ...
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10 votes
3 answers
2k views

Can gusts be reported as lower than wind speed?

KADS 072350Z 31030G20KT 13SM SKC 24/02 A2980 I’ve never seen a negative gust factor before. Is that a real thing (and if so, what does it mean), or did someone just make a typo?
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3 votes
1 answer
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When was the last time the US Standard Atmosphere 1976 was updated?

I imagine due to slight changes in Earth's atmosphere or more accurate instrumentation it's been updated at least once, but also because it's understood to be a less precise model we might not have ...
1 vote
1 answer
134 views

How to get an accurate time of arrival to the en-route alternate airport during flight planning?

I was thinking about accurate criteria of selecting en-route alternate (ERA) weather from ground (planning stage) especially for ERA 3% contingency flight plan. As we all know we should care about one ...
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3 votes
2 answers
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Can I derive the wind speed and direction? [duplicate]

If I know the IAS and GS (with directional components) of an aircraft, can I derive the wind speed and direction? I'm working on an application that simulates the flight of an aircraft. Another ...
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0 votes
1 answer
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What are the Requirements for the implimentation of Low Visibility Procedures at an airport?

So I was wondering if the RVR at an airport is reported above CAT I conditions for eg 1400 Meters etc but the Visibility is 50 to 100 Meters then would the pilots carry out non instrument approach or ...
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5 votes
1 answer
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Why are the airport pressure values for "altitude" (inHg) and "sea level" (mb) slightly different on the NOAA web sites?

If one looks, for example, at the NOAA web site for Denver International Airport we see (at the time of posting this question) the Pressure/Altimeter is 29.78 inHg, the Pressure/sea level is 1006.1 mb ...
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1 vote
0 answers
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A scenario question regarding meteorology

In the image attached, I’m struggling to find out why the answer is the way it is; maybe is me not being able to visualise it, but some help would be greatly appreciated.
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1 answer
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What causes Gusty winds? ( Meteorlogy) [closed]

I was wondering why winds can become gusty. I know that gusty winds tend to be related with frontal passage. Thanks : )
2 votes
3 answers
627 views

What weather should we expect when temperature and dew point are similar?

What should i expect during my flight planning when i see both temperature and dew point are the same? I understand there will be fog but what else? could it mean icing? any difference between 20/20 ...
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1 vote
1 answer
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Why is cloud base estimation taught in Fahrenheit?

I've seen the formula for estimating cloud base consistently presented using Fahrenheit temperature and dewpoint (for example, see PHAK 12-14; Jeppesen also teaches it this way): $$ \mathrm{cloud\:...
3 votes
3 answers
360 views

How can I calculate ambient air pressure from flight data?

I am playing around with data collected during a flight. I would like to find out the (real, not ISA) ambient air pressure for each data point, since it is not reported in the spread sheet containing ...
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2 votes
1 answer
120 views

How can air stability be predicted?

After several weeks of being grounded due to low clouds, I was looking forward to the cool air, clear skies, high pressure and light winds that arrived this morning as forecasted. However, there is an ...
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